• To do this, SIP network

elementsconsult an abstract service known as a location service,

whichprovides address bindings for a particular domain

---10.1 Overview

ReSIProcate的LocationServer类，职责明确

 

• In order to handle the case where an INVITE request never

generatesa final response, the TU uses a timer which is called

timerC. Timer C MUST be set for each client transaction when

anINVITE request is proxied. The timer MUST be larger than 3

minutes.Section 16.7 bullet 2 discusses how this timer is

updatedwith provisional responses, and Section 16.8 discusses

processingwhen it fires.

---11. Set timer C

注：Proxy的int mTimerC;

 

• A dialog is identified at each UA with a dialog ID, which consists of

aCall-ID value, a local tag and a remote tag.

---12 Dialogs

参考resip::DialogId

 

• A dialog contains certain pieces of state needed for further message

transmissionswithin the dialog. This state consists of the dialog

ID,a local sequence number (used to order requests from the UA to

itspeer), a remote sequence number (used to order requests from its

peerto the UA), a local URI, a remote URI, remote target, a boolean

flagcalled "secure", and a route set, which is an ordered list of

URIs.The route set is the list of servers that need to be traversed

tosend a request to the peer.

---12 Dialogs

联系Dum的Dialog类

 

 

 

 

• The client transaction provides its functionality through the

maintenanceof a state machine.

17.1 Client Transaction

注：联想到mStateMacFifo及mStateMachineFifo，附state和machine的值

 typedef enum

      {

         ClientNonInvite,

         ClientInvite,

         ServerNonInvite,

         ServerInvite,

         ClientStale,

         ServerStale,

         Stateless  // may not be needed

      } Machine;

     

      typedef enum

      {

         Calling,

         Trying,

         Proceeding,

         Completed,

         Confirmed,

         Terminated,

         Bogus

      } State;

 

• For any port and interface

   that a server listens on for UDP, it MUSTlisten on that same port

   and interface for TCP.  This is because a message may need to be sent

   using TCP, rather than UDP, if it is toolarge.  As a result, the

   converse is not true.  A server need not listen for UDP on a

   particular address and port just because itis listening on that same

   address and port for TCP.  There may, of course, be other reasons why

   a server needs to listen for UDP on aparticular address and port.

---18.2.1 Receiving Requests

注：前面也多次提到,在某些限制条件下，即便使用UDP传输，SIP Message也不得不通过TCP传输，因此如果配置UDP传输的话，需要同时监视UDP和TCP。不过Resiprocate的proxy似乎没有注意到这一点。